kafka: Add log directory offline status metric

[piochelepiotr]

Summary

• Adds kafka.log.directory.offline metric from kafka.log:type=LogManager,name=LogDirectoryOffline,logDirectory=<path> JMX bean
• Reports whether each log directory is offline (0 = healthy), tagged with log_directory path and kafka_cluster_id
• Useful for monitoring disk health across Kafka brokers

Motivation

Kafka exposes per-log-directory health status via JMX. Monitoring this allows alerting when a log directory goes offline (e.g. disk failure), which can cause data loss if not addressed.

Test plan

• Deploy against a Kafka cluster
• Verify kafka.log.directory.offline is emitted with log_directory tag containing the path
• Confirm value is 0 for healthy directories

🤖 Generated with Claude Code

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 89.03%. Comparing base (3a624a5) to head (e0ad480).
⚠️ Report is 1 commits behind head on master.

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[chatgpt-codex-connector]

Accept unquoted logDirectory in bean regex

The new matcher requires logDirectory="...", but this JMX key is frequently exposed as an unquoted value (for example logDirectory=/var/lib/kafka) depending on Kafka/JMX object-name serialization. In that common case this include rule never matches, so kafka.log.directory.offline is not emitted at all despite being added to metadata/tests. Please make the regex tolerate both quoted and unquoted forms to avoid silently dropping the metric.

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